The present invention relates to an internal combustion engine analyzer and more particularly to an analyzer for use with a computer controlled coil ignition system.
The majority of automotive ignition systems utilize an ignition distributor to control the flow of current between the battery and the sparkplugs. Such distributors consist of a drive shaft with a breaker cam, an advance mechanism, a breaker plate with contact points and a condenser, rotor and cam. The drive shaft is gear driven by the engine cam shaft.
Recently, solid state ignition systems began to appear in automobiles. More particularly, computer controlled coil ignition systems have been developed to eliminate the need for a distributor to control the flow of current between the battery and the sparkplugs. An electro-magnetic sensor consisting of a hall effect sensor, magnet and interrupt ring is utilized to monitor the crank shaft position of the engine. As the crank shaft turns, a signal is produced which gives the top center position of each piston. The crank signal is utilized to develop timing signal for actuating an electronic controlled coil to fire the spark plugs.
However, the advent of computer controlled coil ignition systems has resulted in problems with engine test analyzers which were designed for distributor-type engines. Conventional engine analyzers include monitoring equipment which is connected to the automotive engine to diagnose the engine's operating condition. The apparatus monitors firings of the spark plug for determining proper timing of plug firing. Also, the analyzer may inhibit firing of a selected cylinder for additional testing.
Such engine analyzers look to monitor negative secondary voltages coming from each of the spark plugs and are generally synchronized by separately monitoring the firing of the No. 1 spark plug. The analyzer assumes that the No. 1 spark plug is fired once ever six firings, for example, for a six cylinder engine.
A computer controlled coil ignition system, however, fires half of the spark plugs with a negative firing voltage and the other half with a positive firing voltage. Also, each spark plug is fired in both its compression mode and in its exhaust mode. Thus, the No. 1 cylinder plug is fired twice during the cycle of firing the six cylinders of the engine.
It would be highly desirable to have a separate addon apparatus which may be used with a pre-existing engine test analyzer for permitting the analyzer to test both distributor and distributor-less engines.
It is therefore an object of the present invention to provide an interface apparatus connectable to an engine analyzer when testing a computer controlled coil ignition engine which interface will convert monitored engine signals into signals similar to those monitored in a conventional distributor combustion engine.
It is a further object of the present invention to provide an interface apparatus connectable between an engine analyzer and a computer controlled coil ignition engine for translating information between the engine and the analyzer to provide proper diagnosis by the analyzer.